This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-150004, filed May 22, 2000; and No. 2001-063010, filed Mar. 7, 2001, the entire contents of both of which are incorporated herein by reference.
The present invention relates to a suspension for disc drive incorporated in an information processor such as a personal computer.
A magnetic head is used to record in or read data from a recording surface of a disc in a disc drive that is provided with a rotating magnetic or magneto-optical disc. The magnetic head includes a slider that is opposed to the recording surface of the disc, a transducer in the slider, etc. As the disc rotates at high speed, the slider is slightly lifted off the disc, whereupon an air bearing is formed between the disc and the slider. A suspension for holding the magnetic head is provided with a load beam, a flexure formed of a very thin plate spring fixed to the distal end portion of the load beam, a base plate on the proximal portion of the load beam, etc. The slider that constitutes the magnetic head is attached to the distal end portion of the flexure.
In a hard disc drive (HDD), the track center of the disc should be subjected to following control for xc2x110% or less of the track width. Most of modern high-density discs have a track width of 1 xcexcm or less, so that it is hard to keep the slider in the track center. Accordingly, it is necessary to control the position of the slider more accurately as well as, for example, to increase the rigidity of the disc, thereby damping the oscillation.
In general, conventional disc drives are of a single-actuator type such that a suspension is moved by means of a voice coil motor only. According to this type, a lot of resonance peaks exist in a low-frequency band. It is difficult, therefore, to control the slider (head portion) at the distal end of the suspension in a high-frequency band by means of the voice coil motor only, and the bandwidth of servo cannot be increased.
Accordingly, there has been developed a dual-actuator suspension that is provided with actuator elements, such as piezo-electric elements that are formed of PZT (plumb zircon-titanate), as second actuators. According to this dual-actuator system, only the distal end portion of the suspension or the slider is slightly moved in the width direction (so-called sway direction) of the suspension by means of the actuator elements. A movable part that is driven by means of the actuator elements is considerably lighter in weight than that of the single-actuator system, so that the slider can be controlled in a high-frequency band. Thus, the band width of the servo for slider position control can be made several times as high as that of the single-actuator system, and tracking errors can reduced correspondingly.
FIG. 21 shows a part of a conventional dual-actuator suspension. A micro actuator mechanism 2 of this suspension 1 is formed having slits 4 and 5 in its base portion 3. A pivot portion 7 and support walls 8 and 9 are formed on the proximal portion of a load beam body 6. Actuator elements 10 such as PZT are provided individually on the opposite sides of the pivot portion 7.
One end portion 10a of each actuator element 10 is bonded to the base portion 3, and the other end portion 10b to the load beam body 6. When supplied with current, the actuator elements 10 are distorted in opposite directions. The support walls 8 and 9 bend as this distortion causes the distal end portion of the suspension 1 to be displaced in the sway direction (direction indicated by arrow S) around the pivot portion 7. The suspension of this type will hereinafter be referred to as a pivot-type suspension.
In the pivot-type suspension, the stiffness of the support walls 8 and 9 must be lowered in order to obtain satisfactory displacement in the sway direction. In this case, the torsional stiffness of the whole suspension is reduced, and the sway-mode resonance frequency lowers inevitably. In order to solve this problem, it is necessary to reduce length Lxe2x80x2 and width Bxe2x80x2 of the support walls 8 and 9 and increase the wall thickness.
Since the support walls 8 and 9 are formed integrally with the base portion 3 and the load beam body 6, however, their width Bxe2x80x2 can be reduced only limitedly. Further, their thickness is settled distinctly depending on the respective thicknesses of the base portion 3 and the load beam body 6, so that it is hard to increase the thickness of the support walls 8 and 9.
Since the thickness-direction stiffness of the micro actuator mechanism 2 is low, the PZT elements 10 may possibly undergo deformation such as warping as they are bonded to the base portion 3 and the load beam body 6. If the elements 10 are deformed, their output characteristics may change, or accurate control may fail to be accomplished. Since the elements 10 share a high percentage of load on the micro actuator mechanism 2, moreover, they are damaged heavily when shocked. In some cases, therefore, even a relatively small shock can destroy the elements 10.
Accordingly, the object of the present invention is to provide a suspension for disc drive, in which the resonance peak of the suspension with a micro actuator mechanism can be enhanced, and actuator elements can be made less destroyable.
In order to achieve the above object, a suspension according to the present invention comprises an actuator base including a base plate, a load beam provided with a flexure, and a micro actuator mechanism attached to the actuator base, the micro actuator mechanism including at least one pair of slits formed in the actuator base, a pivot portion situated between the slits, an actuator element provided on the actuator base and adapted to be distorted to cause displacement of the distal end portion of the load beam when supplied with current, and a support wall formed of a bent portion rising in the thickness direction of the actuator base from an edge portion of the actuator base.
In the suspension provided with the micro actuator mechanism of a pivot type, according to this invention, the sway-direction resonance frequency can be increased, so that the position of the suspension can be controlled with higher accuracy.
The pivot-type suspension of the present invention comprises a connecting plate for connecting the actuator base and the load beam, the connecting plate including a main plate portion formed of a plate material thinner than the base plate and superposed on the base plate and the support wall rising in the thickness direction of the main plate portion from an edge portion of the main plate portion, for example. According to this invention, the flexibility of the support wall in the sway direction can be secured.
Further, the connecting plate may be formed of a springy material and include a hinge portion flexible in the thickness direction between the base plate and the load beam. According to this invention, the support wall can be formed by utilizing a part of the connecting plate that integrally has the hinge portion. The support wall is composed of the bent portion that is formed at an end of the thin connecting plate. In this case, the thickness of the support wall can be increased depending on the height of the bent portion. Since the bent portion is thin, moreover, the width of the support wall that is formed of the bent portion can be reduced. Thus, the torsional stiffness and the sway-mode resonance frequency can be enhanced without lowering the flexibility the support wall.
Furthermore, a bending-type suspension for disc drive according to the present invention comprises an actuator base including a base plate having a thickness of 0.17 mm or more and formed integrally with a boss portion, a load beam provided with a flexure, and a micro actuator mechanism attached to the actuator base, the micro actuator mechanism including an actuator element adapted to be distorted to cause displacement of a distal end portion of the load beam when supplied with current.
In the bending-type suspension according to this invention, the sway-direction resonance frequency can be increased, so that the position of the suspension can be controlled with high accuracy. In the suspension of this invention, the actuator elements share lighter load. Since the actuator elements can be protected as they are stored in an aperture of the actuator base, moreover, they can be made less destroyable. Since the actuator elements of this invention are of an embedded type, furthermore, they are arranged substantially symmetrically with respect to the thickness-direction center of the base plate. Accordingly, a displacement obtained when the actuator elements are activated can be effectively transmitted to the distal end portion of the suspension.
The suspension of this invention may comprise a conductive member for electrically connecting a wiring portion on the flexure and a connector portion of the actuator element. According to this invention, the wiring portion on the flexure and the connector portion of the actuator element face on the same side, and they are connected electrically to each other by means of the conductive member, e.g., a bonding wire. Thus, the wiring portion of the flexure and the connector portion of the actuator element can be situated substantially on the same plane with each other, so that the conductive member that connects them need not be long, and connecting operation is easy.
The suspension of the present invention having the actuator element stored in the aperture of the actuator base may comprise a springy connecting plate for connecting the base plate and the load beam to each other, the connecting plate including a hinge portion flexible in the thickness direction between the base plate and the load beam. According to this invention, the base plate and the load beam can be joined to each other by means of the connecting plate that integrally has the hinge portion.
The suspension of this invention may comprise a base plate of a long-mount type attached to a voice coil motor and the micro actuator mechanism on the base plate, the base plate being formed of a cladding material that composed of a light metal and a stainless steel. According to this invention, the whole suspension that has the long-mount base plate can be simplified in configuration and reduced in weight.
Preferably, in the present invention, the base plate, which is provided with the micro actuator mechanism, should have a thickness of 0.17 mm or more. According to this invention, the stiffness of the micro actuator mechanism can be enhanced depending on the thickness of the base plate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.